1. Field of the Invention
The present invention generally relates to optical protection switching architectures, and more particularly to a two-fiber ring architecture providing client connection, ring interconnection, and client self-healing.
2. Technical Background
In the rapid development of highly reliable optical communication systems, networking architectures supporting this increased reliability have become increasingly complex. Ring topologies have arisen to provide a large number of networking elements with the ability to both listen and transmit on optical channels within the optical ring. In such a ring topology, consecutive nodes are connected by point-to-point links which are arranged to form a single closed path or ring.
As optical ring deployment progresses, the transition from small, isolated optical rings will not be to a single ring with a larger xe2x80x9cdiameterxe2x80x9d, but instead to interconnected rings. Thus, single channel lower speed optical ringsxe2x80x94termed xe2x80x9caccess ringsxe2x80x9d xe2x80x94will soon feed higher speed backbone rings in a virtually unlimited array of speeds and sizes. For example, it is quite common today to have xe2x80x9clow-speedxe2x80x9d optical carriers for third level (OC-3) rings feeding OC-48 rings. Both types of rings may even be SONET four-fiber bi-directional line switched rings. In some cases, the OC-48 rings feed an even higher speed OC-192 ring spanning an entire regional service area or crossing national borders. Current approaches, however, continue to involve high costs and limited flexibility. Another difficulty is providing self-healing ring protection for non-SONET signals. More signals can be transported on a 2 or 4-fiber ring by employing wavelength division multiplexing (WDM) to send multiple channels on different wavelengths.
Another particular difficulty is associated with management of the different types of wavelength channels that may be passed among the rings. For example, a client networking element attached to one access ring wishing to communicate with a client networking element attached to another access ring must attempt to pass traffic through the central backbone, or inter-office ring (IOF ring), as well as the interconnection nodes. This technique has resulted in costly ring interconnection designs and a significant difficulty in modifying interconnection sites. Furthermore, failure of a ring interconnection node due to power outages or other problems, typically results in a shutdown of the entire optical ring. All of these shortcomings affect client connection to the ring, ring interconnection, and management of wavelength channels. It is therefore desirable to provide a method and architecture capable of efficiently handling the growing complexity of optical networks.
The above and other objects are provided by a two-fiber ring architecture capable of carrying multiple wavelength channels and allowing client self-healing from single point failures. The ring architecture includes a two-fiber optical ring carrying at least one wavelength channel, where the wavelength channel has working traffic and protection traffic. Specifically, the ring architecture also includes a first client networking element connected to the optical ring by a first add-drop node employing a first pair of 2xc3x972 add drop matrices and a second client networking element connected to the optical ring by a second add-drop node employing a second pair of 2xc3x972 add drop matrices. An interconnect node is also provided, wherein the interconnect node has a first 2xc3x972 interconnect matrix and a second 2xc3x972 interconnect matrix. The first 2xc3x972 interconnect matrix routes the working traffic from the first client networking element to the second client networking element. Similarly, the second 2xc3x972 interconnect matrix routes the protection traffic from the second client networking element to the first client networking element. The optical ring includes a first access ring, an inter-office (IOF) ring, and a second access ring. Access rings are connected to the IOF ring by the aforementioned interconnect nodes.
The interconnect nodes include a first interconnection site and a second interconnection site. The first interconnection site connects working traffic between the IOF ring and one of the access rings. The second interconnection site connects protection traffic between the IOF ring and one of the access rings. The first interconnection site may be physically separate from the second interconnection site for additional protection.
The present invention also provides a method for healing a single point failure in a two-fiber ring, wherein the ring has working traffic and redundant protection traffic. Specifically, the method includes the steps of connecting an upstream client networking element to the ring by a first pair of 2xc3x972 add drop matrices, and connecting a downstream client networking element to the ring by a second pair of 2xc3x972 add drop matrices. Self-healing is effected by performing an electrical switch at the downstream client networking element location from working traffic to protection traffic. The upstream client networking element need only insure that redundant traffic is being transmitted on the protection fiber.